PHYSIOLOGICAL 257 



Rabaud says that "the return to the nest in no way leads us to 

 assume any unknown sense which would merit the name of sense 

 of orientation". He is willing, however, to admit a muscular memory 

 or enregistration of movements. In many cases ants lose their way 

 badly, but against that has to be placed their frequent short-cuts 

 home. Without hesitation they wiU often cut across the hypotenuse 

 of a triangle whose two other sides they described on their outward 

 journey. 



A bee carried from the hive in a box and liberated at a distance 

 of a mile will often rise in the air, circle round a little, and then 

 make a bee-line for home. This seems almost magical, but very 

 careful experiments have made it practically certain that bees 

 build up a general visual impression of their district. "The cues are 

 relations between objects rather than the objects themselves", as 

 is illustrated by their behaviour when the hive is shifted a little 

 during their absence. They persist in going to the place where the 

 hive should have been. 



Within a short distance, the smell of the hive seems to afford a 

 sure clue of a different kind; but the chief clue is visual. Yet the 

 remarkable recent experiments of Wolf suggest that there is more 

 than Rabaud is inclined to allow. Bees were fed at a spot 150 yards 

 north of the hive. Even after short imprisonment in a box none 

 of these bees had any difficulty in flying straight home. But if one 

 was boxed and carried to a spot 150 yards east of the hive and 

 there liberated, it flew 150 yards south and then began to hesitate. 

 After hesitation and circling it proceeded to find its way home by 

 the tentative method of visual search. If carried a couple of miles 

 on to a lake, bees do not "home"; for there are no landmarks on the 

 water. 



The theory of learning the way that applies to ants and bees does 

 not as yet work well in reference to migratory birds. For in many 

 cases the young birds set off by themselves, to all appearance, on 

 their long journey to an unknown goal. 



In the case of the cuckoo, the parent birds leave their progeny 

 behind them to make the long southward journey alone, unless 

 indeed they sometimes get help from their foster-parents. In many 

 birds, moreover, the return route in spring is different from that 

 which is followed in autumn. In a number of cases it has been proved 

 that the young bird, after wintering in the south, returns in spring 

 to the precise place of its birth. 



The migration itself is an hereditarily established racial custom ; 

 and while the way-finding may be in part a response to visual and 

 other stimuli, it is very difficult at present to avoid the conclusion 

 that there is an hereditary memory of the general direction to be 

 followed in the autumnal and vernal flights. 



Rabaud is against the postulate of a special sense; but it remains 



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